This application is based on and incorporates herein by reference Japanese Patent Application No. 2000-209778 filed on Jul. 11, 2000.
1. Field of the Invention
The present invention relates to a method for manufacturing an electromagnetic operating apparatus.
2. Description of Related Art
JP-A-10-299932 discloses an electromagnetic operating apparatus in which a first yoke and a second yoke are formed independently from each other. In the electromagnetic operating apparatus, a bobbin around which a soil is wound supports a plunger as a moving core. Thus, even when axes of the first and second yokes are diverted from each other, the plunger is not prevented from reciprocating.
U.S. Pat. No. 5,769,391 discloses an electromagnetic valve in which an accommodating member and an attracting member are integrally formed to provided a stator core. In the electromagnetic valve, since there is no assembling error, the accommodating member and the attracting member are accurately coaxially arranged. However, when thickness of a connecting portion between the accommodating member and the attracting member is small, the stator core might be transformed by a force forming a resin bobbin at outer peripheries of the accommodating member and the attracting member, or by a force for winding a coil around the bobbin. If the thickness of the connecting portion is set to large for preventing the transformation of the stator core, an amount of magnetic flux flowing between the accommodating member and the attracting member via the connecting portion increases. Whereby, generated magnetic force becomes small relative to an electric current supplied into the coil.
An object of the present invention is to arrange an accommodating member and an attracting member accurately coaxially, and to increase an attracting force generated between the attracting member and a moving core.
According to a first aspect of the present invention, an accommodating base material and an attracting base material, which is independent from the accommodating base material, are resin-insert-molded. After that, the accommodating and attracting base materials are processed to form an accommodating member and an attracting member to accommodate a moving core such that the moving core reciprocates therein. Even if axes of the accommodating base material and attracting base material are diverted from each other when they are insert-molded, the accommodating member and attracting member are accurately coaxially arranged by processing the accommodating and attracting base materials after the insert-molding. Thus, a radial clearance between the accommodating member and the moving core, and between the attracting member and the moving core are made as small as possible, thereby increasing a force attracting the moving core.
According to a second aspect of the present invention, the accommodating and attracting base materials are processed after winding the coil around the bobbin. Thus, a force for winding the coil around the bobbin does not act on the accommodating member and the attracting member. As a result, axes of the accommodating member and the attracting member are prevented from being diverted from each other.
According to a third aspect of the present invention, a stator core base material, which includes base materials of the accommodating member and attracting member, and which includes a thin thick portion integrally formed to connect the base materials to each other, is resin-insert-molded. After that, the resin-insert-molded stator core base material is processed for forming a stator core to accommodate the moving core such that the moving core reciprocates therein. Even when axes of the accommodating base material and attracting base material are diverted from each other due to a pressure during the insert-molding, the accommodating member and attracting member are accurately coaxially arranged by processing the stator core base material after the insert-molding. Thus, a radial clearance between the accommodating member and the moving core, and between the attracting member and the moving core are made as small as possible, thereby increasing a force attracting the moving core.